ANSI/ASHRAE Standard , Thermal Environmental Conditions for Human Occupancy. • Addendum p: Aligns Section with the definition of average. ANSI/ASHRAE Standard (Supersedes ANSI/ASHRAE Standard ). Includes ANSI/ASHRAE addenda listed in Appendix |. o) ASHRAE. Standard — Thermal Environmental Conditions for Human Occupancy( ANSI approved).
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It was first published inand since has been updated every three to six years. The most recent version of the standard was published in The body of the standard consists 55-200 a foreword describing changes made in the current versioneight sections and two normative appendices:. After the body of the standard there are 11 informative appendices.
These are not part of the standard, but provide additional information about terms and methods described 55-210 the standard, as well as a bibliography, and a description of the addenda incorporated from the previous version in the current version.
As described within the standard: The standard addresses the four primary environmental factors temperaturethermal radiationhumidityand air speed and two personal factors activity and clothing that affect thermal comfort. Adaptive model is a model that relates indoor design temperatures or qshrae temperature ranges to outdoor meteorological or climatological parameters.
Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation. A occupant-controlled naturally conditioned space is where the thermal conditions of the space are primarily regulated by occupant-controlled openings.
Comfort zone refers to the combinations of air temperature, mean radiant temperature trand humidity that are predicted to be an acceptable thermal environment at particular values of air speed, metabolic rate, and clothing insulation I cl . Clothing insulation is the resistance to sensible heat transfer provided by a clothing ensemble expressed in units of clo, which is a unit to quantify 552010 insulation provided by garments and clothing ensembles.
Metabolic rate is the rate of transformation of chemical energy into heat and mechanical work by metabolic activities of an individual, per unit of skin surface are expressed in units of met equal to Exceedance hour is the number of occupied hours within a defined time period in which the environmental conditions in an occupied space are outside the comfort zone.
The graphic method utilizes an overlay on a psychrometric chart to indicate the operative temperatures and humidity at which thermal comfort is achieved in the winter 1.
If these requirements are met and the environmental conditions inside the building fall within the indicated ranges, then compliance is achieved. For humidity ratios above 0. Compliance is achieved if the conditions provide thermal neutrality, measured as falling between The section sets provisions for increasing the upper air temperature limit at elevated air speeds above 0.
The methodology is based on the SET Standard Effective Temperature model, which provides a way to assign an effective temperature at a standard metabolic rate, and clothing insulation values to compare thermal sensations experienced at a range of thermal conditions. Radiant temperature asymmetry between asbrae and floor, and air ashdae walls must be limited to reduce discomfort.
ASHRAE 55 – Wikipedia
To reduce draft risk at temperatures below When occupants do not have control over the cyclical variation or drifts in indoor environmental conditions, the conditions within this section must be met. Operative temperatures may not fluctuate more than 1. For this model the standard provides a graph asgrae acceptable indoor temperature limits at prevailing mean outdoor temperatures a mean of the daily mean outdoor temperatures of the previous 7—30 days.
An accompanying table lists provisions for higher operative temperatures at air speeds above 0. The graph is valid for prevailing mean temperatures between 10— This section of the standard is applicable for the design of buildings. All of the building systems must be designed to maintain the occupied spaces at the indoor conditions specified by one of the described evaluation methods at design conditions.
The systems must be able to maintain these asjrae within the expected range of indoor and outdoor operating conditions. To demonstrate compliance the following must be documented, where applicable. Sample documentation is provided in Informative Appendix J. Generally, the evaluation of comfort in existing buildings can be performed from two perspectives: Indoor thermal comfort can be determined from the responses of the occupant survey.
The survey shall be distributed to the entire occupancy or representative part of the occupancy. If that number is between 20 and 45, the minimum number of responses is When the number is under 20, at least 16 must reply for the survey to make the survey representative.
For satisfaction surveys, the thermal satisfaction scale shall end with choices: As for point-in-time surveys, the survey should be solicited during the time of occupancy, and the satisfaction scale ought to be continuous. There should be at least seven points on the scale ending with “very acceptable” and 55-20100 unacceptable. For mechanically conditioned spaces, the PMV-based comfort zone has to be determined, which includes measuring and recording the metabolic activity and clothing insulation.
The comfort zone boundaries must be adjusted to the air movements, and xshrae zone conditions should be adjusted to avoid local thermal discomfort. For occupant-controlled naturally conditioned space, the adaptive model shall be used to determine the thermal comfort boundaries. For such spaces, the indoor and outdoor air temperature and mean radiant temperature and the air speed need to be measured.
The wshrae locations should be where the occupants are expected to spend time in. If there are multiple such locations, the measurement can be performed at a representative location. For seating occupants, the axhrae temperature and air speed measurements shall be taken at heights of 0. The heights need to be adjusted for standing persons. The standard suggests that the time of measurements should last two or more hours long, and it should also be a representative time of the year for this specific building.
Standard 55 – Thermal Environmental Conditions for Human Occupancy
Measuring time step should be no more than five minutes for air temperature, mean radiant temperature, and humidity, and no more than three minutes for the air speed. In order to achieve acceptable results, the standard also suggests the minimum equipment accuracy based the current industry standard. When extracting environmental data from the Building Administration System, one should evaluate the location, height, and time step of the sensors based on the previous suggestion.
To evaluate the probability of satisfaction from satisfaction surveys, the standard suggests dividing the number of the votes falling between “just satisfied” and “very satisfied” by the total number of votes in that questions. The answers of open-ended questions from “very dissatisfied” occupants should be documented for later analysis.
One has to keep in mind that the results from point-in-time surveys are only effective during the time when the surveys were solicited. The measured results should be evaluated against the adjusted comfort zone for the specific building. There are two cases when evaluating thermal comfort: For a mechanically conditioned space at an instance in time, the PMV and SET model shall be used to establish the comfort zone, and the local thermal discomfort shall be evaluated against the limit posed this standard as well.
For occupant-controlled naturally conditioned spaces, the measured results shall be check with the comfort zone established by adaptive model.
To evaluate the thermal comfort over a period of time in a mechanically conditioned space, the exceedance hours are the sum of all the hours when the absolute value of PMV is greater than 0.
For an occupant-controlled naturally conditioned space, the exceedance hours are the sum of hours when the operative temperature falls outside of the lower and upper boundaries of the comfort zone. Metabolic rate is the rate of transformation of chemical energy into heat and mechanical work by metabolic activities of an individual. It is defined as per unit of skin surface area which equals to This is the energy produced from a unit skin surface area of an average person seated at rest.
These values are valid for an average adult ashfae surface skin area of 1. The standard reminds the users that they should use their own judgment to match the activities being considered to the comparable activities in the table. Except sedentary activities, metabolic rate for all other activities is likely to have range of ahsrae. When the duration of an activity is equal or less than one hour, one can use a time-weighted metabolic rate.
As metabolic rates increase over 1.
Clothing insulation refers to the heat transfer of the entire body, which includes the uncovered parts, such as hands and heads. There is a variety of means to determine the insulation provided by clothing. Accurate data from the measurement using thermal manikins is acceptable.
When such measurement is not feasible, this standard provides four methods to determine the clothing insulation. It is also specified that the methods provided by this standard are no longer valid when the clothing insulation exceed 1. And it is also not valid when occupants wear clothing that is highly impermeable to moisture transport. First, one can estimate the clothing insulation from the table provided in section five. If the clothing ensemble in question reasonably matches the clothing ensemble in the table, the indicated value can be used.
Standard 55 – Thermal Environmental Conditions for Human Occupancy
The second method is to add or subtract individual garment clo value to achieve the clothing ensemble in question. This table can be used together with the previous one, so that one can add or subtract the clothing ensemble from the clo value of each garment.
The third method is to add all the clo ashrad of each garment to match the clothing ensemble in question. This method is based on the concept that when occupants choose their clothing according to their environment, the outdoor environment is more influential than the 55-0210 one.
There is a figure in the section five of the standard which predicts the representative clothing insulation of the occupants as a function of the average outdoor air temperature at The function line has four segments: There is a function to determine the representative clothing insulation at each segment.
One can also take into account the posture of the occupants.
So far, all the clothing insulation value can be used when the occupant is standing. When occupant is sitting, one has to realize the insulation effect of the chair, and the decrease of insulation due to compression of the air in the clothing. If the occupant is moving, it also affects the insulation value of clothing. In general, body motion decreases the clothing insulation by pumping air through clothing. Thus, it only provides an approximation of the clothing insulation value of a moving person.
This approximation is an equation that relates the clothing insulation with the metabolic rate. And this equation is only valid when the metabolic rate is between 1. Considering that a sleeping person or one in asjrae posture will be provided with sufficient insulation with the bedding material, and he or she is also free to adjust, it is impossible to determine the clothing insulation effect for these occupants unless they are immobile.
In the first form, different individuals wear different clothing due to factors that are not related to thermal conditions, and the second form is opposite. For the first, it is ashrrae correct to use the average clothing insulation value to determine the desired thermal conditions for all occupants. It was revised in,and In the standard was updated with more extensive information ashae measurement protocols and an expanded definitions section.
In the standard underwent significant changes with the addition of two thermal comfort models: In the standard included the following changes.